I upgraded from f16 to f17 last week, and realized today that valac couldn't be found by the various source tarballs I'm trying to compile. After a bit of investigation, I found that the various vala symlinks in /etc/alternatives/ were still pointing to vala-0.14, which has been replaced by vala-0.16 during the upgrades, leading to broken symlinks.
Ah, yes, the alternatives scriptlets are buggy. I'm testing an update now.
vala-0.16.0-2.fc17 has been submitted as an update for Fedora 17. https://admin.fedoraproject.org/updates/FEDORA-2012-5390/vala-0.16.0-2.fc17
vala-0.14.2-2.fc16 has been submitted as an update for Fedora 16. https://admin.fedoraproject.org/updates/vala-0.14.2-2.fc16
The updated Vala packages have fixed handling of alternatives; people who have 0.14.2-2.fc16 installed before dist-upgrading to fc17 should be fine. Also, I've introduced a workaround that clean up broken symlinks, but for simplicity it'll only clean up one API level (e.g. 0.14 -> 0.16). Since we have not introduced alternatives prior to Fedora 16 (Vala 0.14) that should suffice (I've tested going from 0.14.2-1.fc16 to 0.16.0-2 as well as to 0.16.0-1 -- without the workaround -- and then to -2)
Package vala-0.16.0-2.fc17: * should fix your issue, * was pushed to the Fedora 17 testing repository, * should be available at your local mirror within two days. Update it with: # su -c 'yum update --enablerepo=updates-testing vala-0.16.0-2.fc17' as soon as you are able to. Please go to the following url: https://admin.fedoraproject.org/updates/FEDORA-2012-5390/vala-0.16.0-2.fc17 then log in and leave karma (feedback).
vala-0.16.0-3.fc17 has been pushed to the Fedora 17 stable repository. If problems still persist, please make note of it in this bug report.
vala-0.14.2-3.fc16 has been pushed to the Fedora 16 stable repository. If problems still persist, please make note of it in this bug report.